The purpose of this study is to investigate the diagnostic accuracy of ADC value of diffusion weighted MRI in comparison of conventional treatment assessment criteria in evaluation of chemotherapy. Moreover, the investigators aim to clarify the correlation of ADC value with histologic type and grade of lung cancer and survival of patients.

In recent years, lung cancer is an aggressive and heterogeneous disease, Advances in surgical and chemotherapeutic approaches have been made, but the long-term survival rate remains low. Although effective mass screening of high-risk groups could potentially be of benefit, randomized trials of screening with the use of chest radiography with or without cytological analysis of sputum specimens have shown no reduction in lung-cancer mortality. Currently, Response Evaluation Criteria in Solid Tumors (RECIST) by CT is the most commonly used to evaluate chemotherapy of lung cancer patient, but patients have to be exposed to radiation. For this reason, the investigators aim to assess the diagnostic accuracy of apparent diffusion coefficient (ADC) value, a specific parameter of radiation-free diffusion weighted MRI, in comparison of RECIST, and its correlation with histologic type and grade of lung cancer as well. Furthermore, the investigators investigate its correlation with Progression Free Survival (PFS) and Overall Survival (OS) in patients.

Inclusion Criteria:

1. Age: 18-75
2. Patients have confirmed lung cancer by histopathological methods (fiber, bronchoscopy, lung biopsy, open chest biopsy, pleural effusion exfoliated cells, sputum exfoliated cells)
3. After clinical assessment, patients who need chemotherapy (tumor stage III or IV of lung cancer or others who are reluctant to receive pneumonectomy);
4. Patients have no previous history of chemotherapy
5. Patients with at least one clearly measurable lung lesion (lesion size larger than 10mm, by spiral CT, according to RECIST)
6. Health status scoring between 0-2 by Eastern Cooperative Oncology Group(ECOG) method
7. Patients voluntarily to join this study and signed informed consents.

Exclusion Criteria:

1. Any body metal implants (pacemaker implantation, nerve stimulator, vascular stent, aneurysm clip, eye foreign body, the inner metal prosthesis) or artificial heart valves
2. Patients with claustrophobia to MRI or CT examination
3. Patients who are reluctant to comply with follow-up and subsequent examination
4. The other condition that do not meet the inclusion criteria.